Orcas are known to prey on marine
mammals. This website documents scars on humpback whales caused by
orca bites.

Note the small minke whale sandwiched
between the two G-Pod orcas in
Photo 5. While the photographer did not see the final
outcome of this minke whale/orca encounter, there have been several
reports of orcas killing minkes off St. Anthony (which is where this
photo was take) and other parts of Newfoundland and Labrador.

These photos of the young minke
sandwiched between two larger orcas were taken in July 2005 by Paul
Alcock of Northland Discovery Tours.